Not a single piece of the Boeing 777 has been found, nor any sign of 239 people on board.

Speaking on today's anniversary, Malaysian transport minister Hishammuddin Hussein said: "100 days after MH370 went missing, its loss remains a painful void in the hearts of all Malaysians and those around the world. We cannot rest and will not rest until MH370 is found.

"We cannot and will not abandon the families of the crew and passengers of MH370. We will, with the grace of God, find this missing plane and so with it begins the process of healing."

But, in the absence of any confirmed information, conspiracy theories about what really happened to MH370 have continued to circulate.

"As MH370 was flying 'dar' without a transponder, SIA 68 would have had no knowledge that MH370 was anywhere around as it entered Indian airspace, it would have shown up as one single blip on the radar with only the transponder information of SIA68 lighting up ATC and military radar screens".

This theory was described as feasible but the planes would have to be within 3,300ft of each other.

Alien abduction

Social media users have jumped on the possibility of extraterrestrial life having something to do with the missing plane.

One user wrote: "After an extensive conversation with my father & his partner, we have come to the conclusion that the only explanation is #aliens mh370."

Another added: "I secretly believe that plane is abducted by aliens.. I know I’m not the only one.."

And one user even said there were only two possibilities for its disappearance, aliens or a DB Cooper-style heist.

He wrote: "This Malaysian airlines flight has the potential to be either the greatest heist since DB Cooper, or alien abduction. I vote aliens."

after an extensive conversation with my father & his partner, we have come to the conclusion that the only explanation is aliens #mh370

A life insurance scam

Khalid Abu Bakar addressed the world last month to provide an update on the investigation and revealed authorities were exploring every single avenue - no matter how remote.

"Maybe somebody on the flight has bought a huge sum of insurance, who wants family to gain from it or somebody who has owed somebody so much money, you know, we are looking at all possibilities," he said.

The authorities' investigations extend to examining every detail of the passengers for any clues as to what may have happened.

"We are looking very closely at the video footage taken at the KLIA (Kuala Lumpur International Airport), we are studying the behavioural pattern of all the passengers," he added.

The Illuminati

Reddit users have seemingly taken a keen interest in the disappearance.

One, known only as i-am-SHER-locked apparently uncovered that the Boeing 777 in question was the 404th such aircraft to be produced.

"An HTTP 404 error means not found," they wrote. "Which in this case is oddly appropriate for the status of the aircraft, or just a coincidence.

"Coincidence, I think not."

Edward Snowden

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There were early suggestions 20 employees from the Texas-based Freescale Semiconductor were on board the flight.

So Reddit user Dark_Spectre has put two and two together and come up with, well, you decide.

"So we have the American IBM Technical Storage Executive for Malaysia, a man working in mass storage aggregation for the company implicated by the Snowden papers for providing their services to assist the National Security Agency in surveilling the Chinese," he wrote.

"And now this bunch of US chip guys working for a global leader in embedded processing solutions (embedded smart phone tech and defense contracting) all together..on a plane..And disappeared.. Coincidence??"

He goes on to that the plane itself was kidnapped by Chinese authorities to uncover more about Snowden's revelations.

Electronic warfare experiment

A theory suggesting the plane was hidden as part of an experiment has circulated.

Citizens news site Beforeitsnews.com reported: "It is conceivable that the Malaysia Airlines Flight MH370 plane is 'cloaked', hiding with hi-tech electronic warfare weaponry that exists and is used.

"In fact, this type of technology is precisely the expertise of Freescale, that has 20 employees on board the missing flight."

It also sparked theories the plane could have been taken by North Korea for similarly unknown purposes.

A reddit user wrote: “There’s no telling what crazy logic they [North Korea] might have for taking a plane. They literally have no grasp of reality and have been caught red handed kidnapping foreigners, making s**t up and generally being d****es.”

Fire

One of the most widely held theories is that there was a fire on board that killed all on board but burned out before damaging the exterior of the plane.

This would explain why the aircraft, on auto-pilot, would fly such a long distance off course.

An aviation source said that if this was the case, it would have hit the water at around 600mph after gliding down from 35,000ft.

The source said: “The plane would not have dropped like a stone, it would have glided down from 35,000ft for around 10-12 minutes after it had exhausted its fuel.

“It would have hit the water with a massive impact - as though the plane had landed on concrete. Nobody could have survived that.

“There would have been a huge explosion with the wings ripped off and the fuselage would probably have plummeted straight down.”

A military take out or secret weapon at work

Conspiracy theory and scientific site Natural News, run by Mike Adams, has another theory.

Adams said: “If we never find the debris, it means some entirely new, mysterious and powerful force is at work on our planet, which can pluck airplanes out of the sky without leaving behind even a shred of evidence."

He added: “If there does exist a weapon with such capabilities, whoever controls it already has the ability to dominate all of Earth's nations with a fearsome military weapon of unimaginable power."

He believes the plane fell into an area "outside the search zone" and could lead to a very dark end for Earth.

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Pilot suicide

One explanation for the sudden disappearance, according to some, could be pilot suicide.

But so far no evidence has come to light to suggest either captain Zaharie Ahmad Shah or co-pilot Fariq Abdul Hamid had such intentions.

John Brennan, head of the US Central Intelligence Agency (CIA), told the Daily Mail, when asked if it was a possibility: "I think you cannot discount any theory."

Malaysian police have attempted to investigate whether any passengers or crew on the plane had personal or psychological problems that might shed light on the mystery.

Malaysian police chief Khalid Abu Bakar said at a news conference: "We are looking at all possibilities."

Other theorists have claimed the pilot or crew could have hijacked the plane themselves.

The idea there could be a second Bermuda Triangle seems a popular one on social media.

Its sudden and unexplained disappearance from radar could have several explanations, whether it be a sudden explosion or mid-air disintegration, or even a mechanical failure.

But some theorists believe it simply means the plane has entered another Devil's Triangle.

Boats and planes have been known to disappear in the patch of sea in the North Atlantic Ocean, known as the Bermuda Triangle, including Flight 19 in 1945, when five torpedo bombers mysteriously vanished.

But could there really be another one?

One Twitter user wrote: "So...what is up with this Malaysian airplane thing? Is there an Asian version of the Bermuda Triangle?"